Wyniki wyszukiwania - BazTech

1

Direct conversion of alkaline earth metal hydroxides and sulfates to carbonates in ammonia solutions

Ehsani Ilhan, Ehsani Arman, Ucyildiz Ayse, Obut Abdullah

Physicochemical Problems of Mineral Processing

|

2022

|

Vol. 58, iss. 1

169--180

EN

In this study, the direct conversion behaviors of different alkaline earth metal solids (the hydroxides and the sulfates of alkaline earth metals Ca, Sr, Ba and Mg) to their corresponding carbonates in dissolved carbonate-containing pregnant solutions obtained by direct leaching of a smithsonite (ZnCO3) ore sample in aqueous ammonia solutions having different concentrations (4 M, 8 M and 13.3 M NH3) were investigated by using X-ray diffraction analyses at alkaline earth metal to dissolved carbonate mole ratios of 1:1 and 1:2, for revealing the conversion possibilities of dissolved carbonate in the pregnant solutions to solid carbonate by-products. The results of direct conversion experiments showed that Ca(OH)2, CaSO4•2H2O, Sr(OH)2•8H2O and Ba(OH)2•8H2O converted to their corresponding carbonates, SrSO4 partially converted to SrCO3 as observed by the presence of unreacted SrSO4 peaks in X-ray diffraction patterns of the converted solids, and BaSO4 did not convert to BaCO3 because of its lower solubility with respect to BaCO3. On the other hand, it was observed that Mg(OH)2 did not convert to MgCO3, but MgSO4•7H2O converted dominantly to an uncommon phase, which was tentatively identified as Mg5Zn3(CO3)2(OH)12•H2O. In the study, a complete discussion on the conversion behaviors of alkaline earth metal solids to their corresponding carbonates was given considering the differences between their solubility product constants and the changes in the free energies of the theoretical conversion reactions. In addition, infrared spectra and scanning electron microscope images of some of the converted solids were also presented for characterization purposes.

2

Mechano-chemical conversion of celestite in highly concentrated sodium carbonate media

Sezer Raşit, Arslan Cüneyt

Physicochemical Problems of Mineral Processing

|

2019

|

Vol. 55, iss. 2

324--335

EN

An effect of high-energy ball milling on the mechano-chemical conversion of celestite to strontium carbonate (SrCO3) was studied. A celestite ore was ground by a planetary ball mill in a highly concentrated sodium carbonate (Na2CO3) solution. The experimental study was carried out to determine the effects of milling time (15, 30, and 45 min) and Na2CO3 concentration (1, 1.25, and 1.5 M) on the particle size and SrCO3 percentage of the product. A celestite/ball weight ratio was selected as 1/10 and the volume of carbonate solution was calculated for the stoichiometric amount of sulfate in celestite, as constant. After filtering, washing and drying the precipitated SrCO3 sludge was analyzed by XRD, SEM-EDS. Powders were leached in HCl solution and analyzed by AAS in order to determine the SrCO3 amount in the product. A response surface methodology was applied via the Box-Behnken method for the results of particle size and SrCO3 percentage. Regression model coefficients were 98.61 and 98.14%, which were the results of compatibility as experimentally obtained and predicted by the model, respectively. The maximum amount of SrCO3, 96.84% and the minimum particle size, 10.297 μm were obtained with the maximum values of the parameters, 45 min, 1.5 M Na2CO3, and 450 rpm.

3

Analogowe filtry CMOS w scalonych odbiornikach telefonii bezprzewodowej

Jakusz J., Jendernalik W.

Elektronika : konstrukcje, technologie, zastosowania

|

2007

|

Vol. 48, nr 9

26-30

PL

Na przestrzeni ostatnich lat powstało wiele nowych standardów komunikacji bezprzewodowej, co doprowadziło do zwiększonego zapotrzebowania na przenośne urządzenia wielosystemowe. Tendencja do redukcji poboru mocy, zmniejszania rozmiarów oraz obniżania kosztów produkcji tych urządzeń zmusza do poszukiwania nowych rozwiązań układowych. Jednym z ważniejszych bloków w pełni scalonego odbiornika telefonii bezprzewodowej jest dolnoprzepustowy filtr pasma podstawowego. W artykule omówiono dwa analogowe filtry pasma podstawowego zaprojektowane w Katedrze Systemów Mikroelektronicznych Politechniki Gdańskiej i wykonane w technologii CMOS 0,35 um przez Austriamicrosystems.

EN

Many new standards of cordless communication were introduced within the last years what is leading to increased demand for mobile multiStandard devices. The need to reduce production costs, power dissipation, and sizes of these devices is forcing to develop new circuit solutions for a single-chip transceiver in a CMOS technology. One of that circuit is continuous-time channel-select filter in the front-end of a mobile receiver. This paper presents two realizations of analogue active-RC low-pass channel-select filters in 0.35 um CMOS technology designed at Department of Microelectronic Systems, Gdansk University of Technology, and fabricated by Austriamicrosystems.